How long is it supposed to it take for mono symptoms to go away?

Can be long: It depends on what symptoms you are questioning, but the general sense of being fatigued or run-down, fevers, muscle aches last for 2-4 weeks and the fatigue longer in some cases. It is variable in different people, but get your rest, take care of yourself.

Most 2-3 wks: For most teens or adults this would gradually improve after 2-3 weeks. A subset of <1/4 may have persisting problems for 2-3 mo. There is a myth about a "chronic" mono (yrs) that has been refuted by the CDC.